A complex fluid machine, in which a compressor device, an expansion device, a driving motor and a pump are integrally formed, is known in the art, for example as shown in Japanese Patent Publication No. H8-86289 (a rotating machine of a rolling type piston is shown). In the above complex fluid machine, the respective components are arranged in series and coaxially connected with one another (the compressor device is connected to the expansion device by a magnet coupling device, or directly). The compressor device is used for compressing refrigerant in a refrigerating cycle, whereas the expansion device is operated by working fluid in Rankine cycle.
According to the above fluid machine, the expansion device is driven by the driving motor for a certain period during its initial (starting) stage until an operation of the expansion device becomes stable. Then, the expansion device is driven by the expansion of the working fluid (which is heated by a burner to be converted into high pressure and high temperature working fluid) in the Rankine cycle, so that it is rotated by its own driving force. The driving force is directly or indirectly (through the magnet coupling) transmitted to the compressor device to operate the same, so that the working fluid is compressed. The pump is also operated by the driving force generated at the expansion device for circulating the working fluid in the Rankine cycle.
As above, a heat generating device (such as the burner) is specifically necessary in the above mentioned prior art apparatus. The present inventors have been developing a refrigerating apparatus to be used for an automotive vehicle, in which waste heat from an internal combustion engine is collected and utilized for operating the Rankine cycle, in order that energy consumption can be reduced in view of grovel warming.
In the case that the above mentioned prior art apparatus is used for the automotive vehicle, in which the waste heat from the engine is used as a heating source (instead of the burner), the driving force can not be obtained by the expansion device when an amount of the waste heat from the engine is small. During such a period, the compressor device can be operated by the driving motor. In such a case, however, the pump is also operated by the driving motor together with the compressor device, reducing efficiency of the operation for the compressor by the driving motor.
On the other hand, in the case that the operation of the compressor device is not necessary (a cooling operation by the refrigerating cycle is not required), the operation of the expansion device is stopped even when the waste heat from the engine can be sufficiently obtained. As a result, the waste heat can not be efficiently utilized for collecting the energy by the expansion device.
According to another prior art fluid machine, for example shown in Japanese Patent Publication No. 2004-232492, the fluid machine likewise has a function of a compressor device and a function of an expansion device. According to this prior art fluid machine, the compressor device is also operated as the expansion device, wherein the flow direction of the working fluid in case of operating as the compressor device is opposite to that of the working fluid in case of operating as the expansion device. A first fluid (discharge) port and a first (discharge) valve device are provided in the fluid machine, so that compressed working fluid is pumped out through the first fluid (discharge) port. Further, a second fluid (inlet) port and a second (inlet) valve device are provided in the fluid machine, so that high pressure and high temperature working fluid is supplied into the expansion device. The second fluid (inlet) port is closed by the second valve device (an electrically operated ON-OFF valve device) when the fluid machine is operated as the compressor device.
According to the above fluid device, however, a volume of the second fluid port inevitably becomes a dead volume for a compression operation of the fluid machine (the dead volume: a volume of the working fluid which is not pumped out and remains in a working chamber during the compression operation). It is a problem, in particular, when an inner diameter of the second fluid port is to be designed to be larger for the purpose of allowing a large amount of the working fluid to flow into the working chamber of the expansion device, or when the amount of the working fluid pumped out from the compressor device for each rotation is designed to be smaller.
According to a further prior art refrigerating apparatus, for example shown in Japanese Patent Publication No. S56-43018, the refrigerating apparatus is used for the automotive vehicle, wherein a compressor device is connected with an expansion device so that the compressor device is driven by a driving force generated by the expansion device operated by use of waste heat from an engine. In such a refrigerating apparatus, however, a cooling operation can not be performed in the case that the waste heat can not be collected during a warming up operation of the engine. In particular, even in the case that a large cooling capacity is required for quickly cooling down an inside of the vehicle after the vehicle has been parked under the brazing sun in summer, the cooling operation is not possible so long as the sufficient waste heat can not be collected from the engine.
Therefore, the present inventors have proposed, in their Japanese Patent Application No. 2004-227006, a refrigerating apparatus for an automotive vehicle, in which a compressor device is separated from an expansion device, the compressor device is driven by an engine or a driving motor, and the energy from the expansion device is used for generating an electric power and/or for driving a pump for circulating working fluid in Rankine cycle. According to the above proposed refrigerating apparatus, the cooling operation becomes possible even when there is no waste heat, whereas the energy can be efficiently collected by the Rankine cycle when there is a sufficient amount of the waste heat.
According to the above proposed refrigerating apparatus, however, the cooling operation can not be performed when the engine operation is temporarily stopped, in the case that the refrigerating apparatus is applied to such a vehicle having an idle-stop operation in view of environmental protection.
According to a still further prior art, for example, as shown in Japanese Patent Publication No. 2004-108220, an electric power is generated at a generator which is driven by an expansion device to be operated in Rankine cycle for collecting waste heat.
The electric power generator is usually operated by a sensor-less control method, according to which a rotational phase of the generator is predicted without using a phase sensor, so that a generator of a low cost is realized.
It is not possible, in such a sensor-less control method, to completely prevent an operation of the generator from becoming out of a control as a result the operation steps out of its normal operational condition. Accordingly, the operation of the generator is generally stopped in the case that the operation of the generator (which is driven by the expansion device) steps out of its normal operational condition. Then, since a load to the expansion device is removed, the rotation of the expansion device may be accelerated and may exceed a tolerance rotational level. If it would happen, noise might be generated at the expansion device, and as the case may be, the expansion device might be damaged. Furthermore, a higher voltage may be generated at the generator, causing a problem in that related electrical parts or devices may be damaged.
Even in the case that an operation of the generator is controlled by signals from position sensors, the operation of the generator may become out of control, if a controller (inverter) for the generator becomes out of order, and the rotation of the expansion device may be accelerated and damaged.